T\u1eeb kh\u00f3a t\u00ecm ki\u1ebfm: H\u00e3y Tr\u1ea3 L\u1eddi Em T\u1ea1i Sao? \u2013 T\u1eadp 5 – Arkady Leokum<\/p>\n\n\n\n
K\u1ec3 t\u1eeb n\u0103m 1877 khi Thomas Edison th\u00e0nh c\u00f4ng trong vi\u1ec7c ch\u1ebf t\u1ea1o ra \u201cm\u00e1y\u201d ghi \u00e2m \u0111\u1ebfn nay, m\u00e1y n\u00e0y \u0111\u00e3 \u0111\u01b0\u1ee3c c\u1ea3i ti\u1ebfn kh\u00f4ng ng\u1eebng v\u00e0 r\u1ea5t mau l\u1eb9 \u0111\u1ea1t \u0111\u01b0\u1ee3c nh\u1eefng th\u00e0nh t\u1ef1u r\u1ef1c r\u1ee1 \u0111\u1ebfn n\u1ed7i h\u1ea7u nh\u01b0 ta kh\u00f4ng c\u00f2n nh\u1eadn th\u1ee9c ra b\u01b0\u1edbc kh\u1edfi \u0111\u1ea7u c\u1ee7a n\u00f3.<\/p>\n\n\n\n
M\u00e1y ghi \u00e2m b\u1eb1ng b\u0103ng nh\u1ef1a l\u00e0 m\u1ed9t trong nh\u1eefng th\u00e0nh t\u1ef1u cao nh\u1ea5t trong l\u0129nh v\u1ef1c n\u00e0y. \u00c2m thanh \u0111\u01b0\u1ee3c ghi l\u1ea1i th\u00f4ng qua kh\u00f4ng ph\u1ea3i b\u1eb1ng m\u1ed9t m\u00e0 b\u1eb1ng hai, ba, b\u1ed1n, micro v\u00e0 \u0111\u01b0\u1ee3c ghi tr\u00ean b\u0103ng t\u1eeb (magnetic tape). V\u00e0 \u00e2m thanh \u0111\u00e3 \u0111\u01b0\u1ee3c bi\u1ebfn \u0111\u1ed5i th\u00e0nh t\u00edn hi\u1ec7u \u0111i\u1ec7n t\u1eed. Nh\u1eefng t\u00edn hi\u1ec7u n\u00e0y t\u1ea1o ra nh\u1eefng \u201ch\u1ea1t\u201d \u0111\u01b0\u1ee3c \u201ct\u1eeb h\u00f3a\u201d tr\u00ean b\u0103ng t\u1eeb theo m\u1ed9t ph\u01b0\u01a1ng ph\u00e1p \u0111\u1ed9c \u0111\u00e1o. Khi quay b\u0103ng nh\u1eefng \u201ch\u1ea1t\u201d b\u1ecb t\u1eeb h\u00f3a s\u1ebd l\u1ea1i ph\u00f3ng ra nh\u1eefng t\u00edn hi\u1ec7u \u0111i\u1ec7n t\u1eed nguy\u00ean th\u1ee7y. V\u00e0 nh\u1eefng t\u00edn hi\u1ec7u n\u00e0y s\u1ebd \u0111\u01b0\u1ee3c \u0111\u1ed5i tr\u1edf l\u1ea1i th\u00e0nh \u00e2m thanh.<\/p>\n\n\n\n
Ng\u01b0\u1eddi ta d\u00f9ng b\u0103ng t\u1eeb \u0111\u1ec3 ghi \u00e2m v\u00ec n\u00f3 (b\u0103ng t\u1eeb) c\u00f3 th\u1ec3 \u201cr\u00e1p n\u1ed1i\u201d \u0111\u01b0\u1ee3c. Ngh\u0129a l\u00e0 c\u00f3 th\u1ec3 c\u1eaft b\u1ecf \u0111o\u1ea1n m\u00e0 ta kh\u00f4ng th\u00edch \u0111\u1ec3 thay v\u00e0o \u0111\u00f3 b\u1eb1ng \u0111o\u1ea1n ta th\u00edch h\u01a1n.<\/p>\n\n\n\n
\u00c2m thanh \u0111\u01b0\u1ee3c truy\u1ec1n qua b\u1ed9 ph\u1eadn ghi. B\u1ed9 ph\u1eadn n\u00e0y s\u1ebd kh\u1eafc l\u00ean m\u1ed9t c\u00e1i d\u0129a \u0111\u01b0\u1ee3c ch\u1ebf t\u1ea1o \u0111\u1eb7c bi\u1ec7t, h\u01a1i \u201cm\u1ec1m\u201d v\u00e0 \u0111\u01b0\u1ee3c ph\u1ebft m\u1ed9t ch\u1ea5t \u201cs\u01a1n\u201d \u0111\u1eb7c bi\u1ec7t. S\u1ee9c \u00e9p v\u00e0 h\u01a1i n\u00f3ng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong qu\u00e1 tr\u00ecnh ghi \u00e2m l\u00ean \u201cd\u0129a\u201d. T\u1eeb d\u0129a n\u00e0y, ng\u01b0\u1eddi ta t\u1ea1o ra \u201cb\u0103ng c\u00e1i\u201d. V\u00e0 t\u1eeb \u201cb\u0103ng c\u00e1i\u201d n\u00e0y, ng\u01b0\u1eddi ta \u201csang\u201d ra th\u00e0nh nhi\u1ec1u b\u1ea3n t\u1ee9c l\u00e0 c\u00e1c b\u0103ng m\u00e0 ch\u00fang ta d\u00f9ng. \u0111\u00f3 l\u00e0 c\u00e1ch ghi \u00e2m tr\u00ean b\u0103ng t\u1eeb. Tuy nhi\u00ean c\u00e1c m\u00e1y cas- sette s\u1ebd ch\u1eb3ng \u0111\u01b0\u1ee3c ph\u1ed5 bi\u1ebfn r\u1ed9ng r\u00e3i nh\u01b0 ng\u00e0y nay n\u1ebfu ng\u01b0\u1eddi ta kh\u00f4ng ch\u1ebf t\u1ea1o ra \u0111\u01b0\u1ee3c b\u0103ng t\u1eeb. S\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a b\u0103ng t\u1eeb ng\u00e0y nay l\u00e0 k\u1ebft qu\u1ea3 c\u1ee7a m\u1ed9t qu\u00e1 tr\u00ecnh nghi\u00ean c\u1ee9u c\u00f4ng phu l\u00e2u d\u00e0i qua bi\u1ebft bao n\u1ed7 l\u1ef1c c\u1ea3i ti\u1ebfn v\u00e0 ho\u00e0n thi\u1ec7n. L\u00fac \u0111\u1ea7u l\u00e0m g\u00ec \u0111\u00e3 c\u00f3 b\u0103ng t\u1eeb b\u1eb1ng ch\u1ea5t d\u1ebbo nh\u01b0 ng\u00e0y nay. T\u1eeb b\u0103ng c\u00e1i, ng\u01b0\u1eddi ta \u201csang\u201d ra nh\u1eefng b\u0103ng con tr\u00ean nh\u1eefng cu\u1ed9n\u2026 d\u00e2y kim lo\u1ea1i, v\u00e0 sau \u0111\u00f3 l\u00e0 tr\u00ean nh\u1eefng \u201cb\u0103ng kim lo\u1ea1i\u201d. Tuy nhi\u00ean k\u1ebft qu\u1ea3 kh\u00f4ng m\u1ea5y kh\u1ea3 quan.<\/p>\n\n\n\n
Sang Th\u1ebf chi\u1ebfn th\u1ee9 hai, khi qu\u00e2n \u0111\u1ed3ng minh ti\u1ebfn v\u00e0o n\u01b0\u1edbc \u0111\u1ee9c qu\u1ed1c x\u00e3 ng\u01b0\u1eddi ta t\u00ecm th\u1ea5y nh\u1eefng cu\u1ed9n b\u0103ng ghi \u00e2m v\u1edbi ph\u1ea9m ch\u1ea5t r\u1ea5t cao \u0111\u01b0\u1ee3c d\u00f9ng trong c\u00e1c \u0111\u00e0i ph\u00e1t thanh c\u1ee7a \u0111\u1ee9c. C\u00f3 \u0111i\u1ec1u ng\u01b0\u1eddi ta v\u1eabn ch\u01b0a n\u1eafm \u0111\u01b0\u1ee3c \u201cb\u00ed quy\u1ebft\u201d ch\u1ebf t\u1ea1o lo\u1ea1i b\u0103ng n\u00e0y. Nh\u01b0ng k\u1ec3 t\u1eeb khi ph\u00e1t minh ra b\u0103ng l\u00e0m b\u1eb1ng nh\u1ef1a d\u1ebbo th\u00ec ng\u00e0nh thu b\u0103ng v\u00e0 ch\u1ebf t\u1ea1o m\u00e1y cassette \u0111\u00e3 c\u00f3 nh\u1eefng b\u01b0\u1edbc ti\u1ebfn kh\u1ed5ng l\u1ed3. \u00c2m thanh tr\u00ean b\u0103ng \u0111\u01b0\u1ee3c \u201ct\u1eeb h\u00f3a\u201d b\u1edfi nh\u1eefng h\u1ea1t \u0111\u00e3 \u0111\u01b0\u1ee3c t\u1eeb h\u00f3a. Do \u0111\u00f3, ta c\u00f3 th\u1ec3 x\u00e0i (quay) \u0111\u1ebfn h\u00e0ng ng\u00e0n l\u1ea7n m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng bao nhi\u00eau \u0111\u1ebfn ch\u1ea5t l\u01b0\u1ee3ng \u00e2m thanh. \u0111i\u1ec1u n\u00e0y kh\u00e1c v\u1edbi c\u00e1ch ghi \u00e2m tr\u01b0\u1edbc kia. Tr\u01b0\u1edbc kia, khi c\u00e1c \u201cr\u00e3nh\u201d ghi \u00e2m b\u1ecb kim \u201cch\u00e0 s\u00e1t\u201d nhi\u1ec1u l\u1ea7n th\u00ec s\u1ebd b\u1ecb r\u1ed9ng ra, do \u0111\u00f3 ch\u1ea5t l\u01b0\u1ee3ng \u00e2m gi\u1ea3m \u0111i r\u1ea5t nhi\u1ec1u. Ngo\u00e0i ra ng\u01b0\u1eddi ta c\u00f2n c\u00f3 th\u1ec3 \u201ct\u1ea9y x\u00f3a\u201d t\u1eebng \u00e2m thanh kh\u00f4ng \u01b0ng \u00fd b\u1eb1ng c\u00e1ch \u201ckh\u1eed t\u1eeb\u201d (demagnetized) v\u00e0 thay v\u00e0o \u0111\u00f3 t\u1eebng \u00e2m thanh kh\u00e1c.<\/p>\n","protected":false},"excerpt":{"rendered":"
T\u1eeb kh\u00f3a t\u00ecm ki\u1ebfm: H\u00e3y Tr\u1ea3 L\u1eddi Em T\u1ea1i Sao? \u2013 T\u1eadp 5 – Arkady Leokum K\u1ec3 t\u1eeb n\u0103m 1877 khi Thomas Edison th\u00e0nh c\u00f4ng trong vi\u1ec7c ch\u1ebf t\u1ea1o ra \u201cm\u00e1y\u201d ghi \u00e2m \u0111\u1ebfn nay, m\u00e1y n\u00e0y \u0111\u00e3 \u0111\u01b0\u1ee3c c\u1ea3i ti\u1ebfn kh\u00f4ng ng\u1eebng v\u00e0 r\u1ea5t mau l\u1eb9 \u0111\u1ea1t \u0111\u01b0\u1ee3c nh\u1eefng th\u00e0nh t\u1ef1u r\u1ef1c r\u1ee1 \u0111\u1ebfn […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15],"tags":[],"class_list":["post-14606","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/14606","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=14606"}],"version-history":[{"count":1,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/14606\/revisions"}],"predecessor-version":[{"id":14607,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/14606\/revisions\/14607"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=14606"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=14606"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=14606"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}